Based on your description of a good pedal, then it goes to the floor after waiting 15 seconds, it sounds like the rear shoes are out of adjustment. After pressing the pedal once, it will come back up faster than the brake fluid can return from the rear so the shoes are partially applied when you press the pedal again and take a new bite of fluid. The shoes will move out a little further each time you pump the pedal until they contact the drums. That's when the pedal will become firm. When you release the pedal for more than a few seconds that gives the shoes time to fully retract. Then the pedal will go to the floor again.

Answered by caradiodoc (expert)
17,285 answers provided

Hey thanks for the reply, I actually figured it out the very next day. Believe it or not, I actually had to take the calipers back off, remove the pads and bench bleed each caliper 3 times. I have done a hundred brakes, and NEVER had to do that before. For some reason the fluid wasnt pushing all the air out of the bleed valve. So that is now a NOTE TO SELF.

Response from JUS 10 TIME
3 questions asked

Happy to hear it's fixed. Any chance the calipers were on the wrong side putting the bleeder screws on the bottom? Sounds silly but that's what someone else found a few weeks ago.

Answered by caradiodoc (expert)
17,285 answers provided